Liquid crystalline azoxybenzene compounds

ABSTRACT

Novel p, p&#39;&#39;-di-n-alkyl azoxybenzenes containing 4 to 10 carbons in the alkyl groups have been found to be liquid crystalline having transition temperatures above their melting points.

a smRcH XE 3 9 9 (3 7 9 7G8- Unlted State 1111 3,907,768

van der Veen et al. SUBSTITUTE FOR MlSSlNG XR [45] P 1975 [5 LIQUID CRYSTALLiNE AZOXYBENZENE 3,532.642 10/1970 Furukawa 61 al. 260/143 x COMPOUNDS OTHER PUBLICATIONS [751 lnvemors= Jan Newbold et al., Chemical Abstracts. v61ume 60,

Hendnkus Grobben, both of 1 ]922f (1964) v Emdhoven Netherlands Ruechardt et al.. Chemical Abstracts, Volume 57, [73] Assignee: U.S. Philips Corporation, New 16474d (1962).

York Ber. Deut. Chem. GeslL, Du Toit Malherbe, Volume 221 Filed: Mar. 31, 1972 Pages 319 to 324 (1919)- Houben-Weyl, Methodischen Der Organischcn Che- 240171 mie v61um6 10/3. pages 762 to 767 (1965).

[30] Foreign Application Priority Data Primary Examiner-Floyd D. Higel Apr. 3, 1971 Netherlands 7104498 Attorney, g or -Fran Trifuri; rman N. Spain [52] U.S. Cl 260/143; 260/205; 260/562 R;

260/578; 260/592; 252/408; 350/160 R [57] ABSTRACT 51 int. c1. c07c 105/00 158 Field 61 Search 260/143 Novel P P amxybenzenes conmnm'g 4 I l0 carbons in the alkyl groups have been found to he [56] References Cited I lig uid crlys talline having transition temperatures above UNITED STATES PATENTS m poms 3.467.688 9/1969 Putnam et al 260/l43 x 9 Claims 2 Drawing F igures LIQUID CRYSTALLINE AZOXYBENZENE COMPOUNDS The invention relates to novel liquid crystalline azoxy compounds.

Several azoxy benzene compounds which are substituted by a polar group in both para positions and have liquid crystalline properties have been described, for example p,p'-dimethoxyazoxybenzenc and p,p'-dihexyloxyazoxybenzene (for example in J. Org. Chem. 33 591-597 (l968)). Hitherto it has been assumed that the presence of polar substituents is a condition for liquid crystalline properties (G. W. Gray, Molecular Structure and Properties of Liquid Crystals, London/- New York (1962) page 184).

It has indeed been found that azoxybenzenes substituted by apolar groups, such as p,pdimethylazoxybenzene and p,p-diethylazoxybenzene, are not liquid crystalline.

Surprisingly the novel p,p'-di-n.alkylazoxybenzenes in which the alkyl groups contain from 3 to carbon atoms have been found to be liquid crystalline. Although these compounds themselves do not exhibit dynamic scattering" in a static or alternating electric field, it was found that mixtures of the novel azoxybenzenes with liquid crystalline azomethines, such as those described in French Pat. specification No. 1,537,000, Dutch Pat. application No. 7,007,0l2, German Prepublished Pat. application Nos. 1,928,242, 2,017,727 and 2,038,780, do exhibit dynamic scattering. Moreover the admixture of azomethines increases the temperature range within which the azoxybenzenes are liquid crystalline.

Accordingly the invention relates to novel azoxybenzene compounds of formula 1 where R and R each represent a n-alkylgroup containing from 3 to 10 carbon atoms, to mixtures of the compounds and to mixtures with liquid crystalline azomethines.

It should be noted that, as described in Mikrochemie, Mikrochimica Acta 38 376-380 1951 p,p-dimethyldiazoxybenzene is alleged to be crystalline between 698C and the melting point 70C. Apart from the fact that a compound which is liquid crystalline within a range of 0.2C would be unsuitable for use in practice, a liquid crystalline nature is erroneously ascribed to the said compound. It is ascerted that liquid crystalline" regions were observed on slow cooling of the melt. Probably, however, the formation of very small crystals gave rise to this erroneous interpretation. If in a prepal0 ration of homogeneous composition and homogeneous temperature distribution, such as a slowly cooled melt, liquid crystalline phenomena occur, they extend through the entire preparation and are not restricted to small regions.

The compounds according to the invention are partly nematic and partly smectic. Some have both a smectic and a nematic range.

In Table 1 compounds according to the invention and their liquid crystalline properties are listed.

mam

N/l transition temperature nematic-isotropic S/N transition temperature smectic-nematic S/l transition temperature smectic-isntropic.

The nematic liquid crystalline temperature range of p,p'-di-n.butylazoxybenzene l 827C) is increased to from 5 to 10C 42C by the admixture of 0.4 mole of 4'-methoxybenzylidene-4-butyloxyaniline.

On admixture of 1 mole of 4-ethoxybenzylidene-4- 45 n.butylaniline the liquid crystalline range of the substance extends from 3C to +45C.

Table 2 gives some mixtures of compounds of the formula I.

TABLE 2 substance A substance B substance C Ratio A/B/C M.P., C N/l "C SIN "C R, R R. R R. R

C.H C,-,H-, 2 moles/ 3.5-4.5 33

l mole 4 a s n l0 parts If) 58 by weight 90 parts by weight s n a m 1 mole/ 9 1 mole s n CGHH 3 moles/ 8 57 1 mole s n c n l molc/ I I2 53 3 moles 4 u C,H C H l mole/ 2 +2 52 l molc/ l mole C1 1 Ct 2 moles/ 5 10 38-39 13 1 mole G C,H,, 1 mole/ 2 6 48-49 5 1 mole C H /C;H 4-components, Example 4. 8 -'+2 4l 42 Compounds and mixtures according to the invention may be used in E.S.R. (electron spin resonance) and N.M.R. (nuclear magnetic resonance) measurements, in gas chromatography and in displays.

The novel azoxybenzenc compounds may be produced by methods known for the production of compounds of this type and by analogous methods.

A suitable method is that in which a compound of the formula 2 where R and R have the same meanings as in formula 1, is oxidized. The reaction is preferably carried out with hydrogen peroxide. The solvent used preferably is glacial acetic acid.

The compound of the formula 2 are obtainable by acctylating n.alkylbenzene with acetylchloride or acetic acid anhydride, using AICL, as a catalyst. The pn.alkylacctophenoncs obtained are then converted in a Schmidth reaction with sodium azide into p-n. alkylacetanilides, which subsequently are hydrolysed. The resulting p-n.alkylanilines or mixtures of palkylanilines may then be oxidized with active M110 to form the compounds of the formula 2.

The compounds of the formula 1 are also obtainable by oxidizing p-n-alkylanilines of the formula 3 or mixtures of p-n-alkylanilincs. This reaction is preferably carried out with hydrogen peroxide, for example with acetonitrile as a co-oxidant.

FIG. 1 is a plan view of the display before the polar ization screens are applied,

FIG. 2 is a cross-sectional view taken on the line AB after that the polarization screens have been applied.

EXAMPLES la. pn.propylacetophenone 42.6 ml of acetylchloride was added drop by drop with vigorous stirring to a suspension of 80 g of of aluminium chloride in 350 ml of carbon tetrachloride, care being taken to ensure that the temperature of the solution did not exceed C. Subsequently under the same conditions 60 g of n-propylbenzene was added drop by drop over a period of 3 hours. after which stirring was continued for 1 hour. The reaction mixture was poured in a mixture of 500 g of ice and 250 ml of concentrated hydrochloric acid. The organic layer was separated and successively agitated twice with 250 ml of 2N hydrochloric acid. once with 250 ml of a saturated sodium carbonate solution and once with 250 ml of water. After drying for 3 hours on a molecular sieve of mesh width 4 A the carbon tetrachloride was distilled off and the residue was distilled under reduced pressure. Boiling point 8290C (0.9l.0 mm of Hg).

lb. p-nipropylacetanilide 7 g of sodium azide was added with vigorous stirring to a solution of l6.2 g of p-npropylaeetophenone in 146 ml of 70?! H 50. in an hour at a temperature of from l5 to C. 50 ml of mcthylenechloride was added to prevent foaming. The mixture was stirred for half an hour. Then the reaction mixture was poured in 200 ml of ice water and lOO ml of methylene chloride. The aqueous layer was separated and extracted twice with ml portions of methylene chloride. The collected methylene chloride extracts were agitated with 50 ml of a saturated sodium carbonate solution and 50 ml of water. 150 ml of methylene chloride was distilled off and the residual solution was poured in 200 ml of petroleum ether (boiling point 80C). The resulting residue was filtered off and dried under reduced temperature.

Melting point 985 995C.

lc. p-n.propylartiline A mixture of 58 g of p-n-propylacetanilide, 552 ml of ethanol, 275 m] of sodiumhydroxide and l72 ml of water was boiled at a reflux cooler for 5V2 hours. The ethanol was then distilled off until the bottom temperature was 94C. The residue was poured in a mixture of 600 g of ice and 400 ml of water. This liquid was extracted with 400 ml of benzene and twice with 200 ml portions of benzene. The benzene extracts were washed twice with portions of 200 ml water and then dried over potassium carbonate. The benzene was then distilled off and the residue was distilled under reduced pressure.

Boiling point 60 62C (0.5 0.55 mm of Hg).

1:1. p,p-di-n.propylazoxybenzene A mixture of 20.5 g of acetonitrile, 200 ml of methanol and l2.4 g of p.n.propylaniline was heated to from 35 to 40C and the pHvalue was brought to 9.5 by the addition of 2 N sodium hydroxide. This temperature and pH-value were carefully maintained during the entire reaction. Then 68 ml of a 30 hydrogen peroxide solution was added with vigorous stirring in an hour. Subsequently stirring wascontinued for 5 hours. After the mixture had been allowed to stand for a comparatively short time the above-mentioned liquid was decanted and the residual oil was subjected to steam distillation The residue of the steam distillation was recrystallized from methanol-ethanol (l 1).

Melting point 65 66C 2. The compounds listed in Table 2 were prepared by analogous methods,

3a. p,p-di-n.-butylazobenzene A mixture of 7.45 g of p-n.butylaniline, 26 g of manganese dioxide and 250 ml of benzene was boiled at a reflux cooler with vigorous stirring for 6 hours, the

water being removed azeotropically. Subsequently the manganese dioxide was filtered off and the benzene was distilled off. The residue was recrystallized from The above mixture was obtained from 7.45 g of pn.butylaniline and 8.15 g of p-n-pentylaniline by a method analogous to that described in Example 1. Melting point from -8C to +2C.

5. A glass plate of 60 X 65 X 2 mm (1 in FIGS. l and 2) provided with a pattern of indium oxide in the form of a figure 8 comprising seven segments 2 and a second glass plate of 50 X 60 X l mm 3 coated with a film of tin oxide 4 of thickness 0.l ,um were rubbed on their oxide-covered sides with a piece of lens tissue in one direction: plate 1 in the direction of its length, plate 3 in the transverse direction.

Two strips of polythene 5 of thickness 20 ,um were laid on plate 1, after which plate 3 was laid' on the strips. The layers were joined to one another by means of an epoxy adhesive 6 with the formation of filling apertures 7. The space between the glass plates was filled with p.p'-di-n-butylazoxybenzene. The apertures 7 were then closed with the adhesive.

Current supply leads were connected to indiumoxide terminal pads 8 and to the part of plate 3 projecting beyond plate 1. To the lower surface of plate 1 and to the upper surface of plate 3 planepolarization screens 9 were applied so that their directions of polarization were parallel to one another and to the rubbing direction of the plate 1. The resulting display when viewed through showed a dark image field.

The dibutylazoxybenzene molecules lie at the surfaces of the plates 1 and 3 in a direction parallel to the surfaces and to the direction of rubbing. Because these directions are at right angles to one another, the liquid crystalline compound has a twisted nematic structure.

An alternating voltage of 6 volts, 50 Hz, was set up across the glass plate 3 and the segments 2 on the plate where R and R each represent a normal alkyl group containing from 4 to l0 carbon atoms and mixtures thereof.

2. A compound of the formula where R and R each represent a normalmlkylgroup containing from 4 to l0 carbon atoms.

. The 4,4'-di-n.butylazoxybenzene of claim 2.

. The 4,4'-di-n.pentylazoxybenzene of claim 2.

. The 4,4'-di-n.hexylazoxybenzene of claim 2.

. The 4,4-di-n.heptylazoxybenzene of claim 2.

. The 4,4-di-n.octylazoxybenzene of claim 2.

. The 4,4-di-n.nonylazoxybenzene of claim 2. 

1. A MEMBER SELECTED FROM THE GROUP CONSISTING OF A COMPOUND OF THE FORMULA
 2. A compound of the formula
 3. The 4,4''-di-n.butylazoxybenzene of claim
 2. 4. The 4,4''-di-n.pentylazoxybenzene of clAim
 2. 5. The 4,4''-di-n.hexylazoxybenzene of claim
 2. 6. The 4,4''-di-n.heptylazoxybenzene of claim
 2. 7. The 4,4''-di-n.octylazoxybenzene of claim
 2. 8. The 4,4''-di-n.nonylazoxybenzene of claim
 2. 9. The 4,4''-di-n.decylazoxybenzene of claim
 2. 